OK, starting a new thread fueled from the discussion in Notnyt's thread. LTD02 kindly offered to take a stab at designing a 6th order band pass sub. I am looking for full output right down to at least 5hz or lower if I can.

So LTD02, what do you need to get this started? I have a storage area in the back of my theater which my second IB is installed, it is about 1,200 cubic feet.

just looking at some initial models, i'm not sure a 6th order bandpass is going to make you very happy.

for the upper tuned port to contribute much, it has to be fairly close to the lower tune and then spl rolls off quickly above whatever point is chosen. doubling the frequency is still reasonably close and in beast's build that was about 12hz lower / 25hz upper. here it would be ~5hz lower and about 10hz upper, so rolloff would start there and go down. seems like too much wasted bass to me.

however, just a big ole standard ported will pick up about 12db or so around the tuning frequency and that is significant with no loss in spl above the tuning frequency. so maybe that is the best option...at least so far. 12db is more or less the same as four times the drivers and four times the power.

very rough draft, first pass look.

in order to keep port velocity down with 3 drivers, a rather large port may be required. this may be the first build that uses full size sonotube for the port.

but at these frequencies, and at this scale, i'm also not sure which room is actually being ported. that is actually something that i never thought about...if the rear and the front room are both the same size, does the port somehow get another 6db or something from both rooms resonating at the same frequency?

in any case, here are some max spl plots for 3 xxx sealed, ported at couple different frequencies, and 6th order.

BTW, that pic is an old one, it best represents the opening I have. I actually have 4 of the drivers.

I agree. I am not really liking those numbers. How long would a port have to be to tune to 5hz? Could I make the whole space act like a box sub? I can effectively completely seal the space as good as a boxed sub due to it being soild concrete walls ,floor and ceiling. I also have a sealed sound proof door which is air tight as well.

but at these frequencies, and at this scale, i'm also not sure which room is actually being ported. that is actually something that i never thought about...if the rear and the front room are both the same size, does the port somehow get another 6db or something from both rooms resonating at the same frequency?

Fascinating question.

One thing which would seem to be the case is that equal volumes on both sides of the port means equal air springs on both sides, so the port will have to be longer.

Hey man, just was thinking about this in another thread. Hope I don't sound like a salesman by now but if you have the cash get a rotary woofer to fill in below 20Hz. You certainly have the volume in your storage area. Just sayin..

SXRDork: SXRD is a technology. My name is Vann. Usernames are for life...

Hey man, just was thinking about this in another thread. Hope I don't sound like a salesman by now but if you have the cash get a rotary woofer to fill in below 20Hz. You certainly have the volume in your storage area. Just sayin..

Actually, I have seriously thought about doing that, I am just not sure about having them come all the way to Japan to do the install.

just looking at some initial models, i'm not sure a 6th order bandpass is going to make you very happy.

for the upper tuned port to contribute much, it has to be fairly close to the lower tune and then spl rolls off quickly above whatever point is chosen. doubling the frequency is still reasonably close and in beast's build that was about 12hz lower / 25hz upper. here it would be ~5hz lower and about 10hz upper, so rolloff would start there and go down. seems like too much wasted bass to me.

however, just a big ole standard ported will pick up about 12db or so around the tuning frequency and that is significant with no loss in spl above the tuning frequency. so maybe that is the best option...at least so far. 12db is more or less the same as four times the drivers and four times the power.

very rough draft, first pass look.

in order to keep port velocity down with 3 drivers, a rather large port may be required. this may be the first build that uses full size sonotube for the port.

but at these frequencies, and at this scale, i'm also not sure which room is actually being ported. that is actually something that i never thought about...if the rear and the front room are both the same size, does the port somehow get another 6db or something from both rooms resonating at the same frequency?

in any case, here are some max spl plots for 3 xxx sealed, ported at couple different frequencies, and 6th order.

I was thinking about this when the first 6th order bandpass thread originated. Specifically, I was thinking about porting my IB subs to give me more 7 Hz where my electronics were rolling off big time (or so I think). My storage room is approximately 1200 cu. ft. but it is a little difficult to determine the exact volume. I noticed in the simulations that the difference in port length to get the tuning frequency I wanted changed significantly with enclosure volume. If I remember correctly, I'm talking about a 6-7 inch port at 1000 cu. ft. versus a 4-inch port with 1200 cu. ft.

I'm pretty sure I've decided not to do it due to the sensitivity of tuning frequency with IB volume. You may want to consider this.

SXRDork: SXRD is a technology. My name is Vann. Usernames are for life...

"I'm pretty sure I've decided not to do it due to the sensitivity of tuning frequency with IB volume."

that's not a show stopper by any means. just build and test a couple ports to dial in the length to hit your target tuning. around tuning the driver will move very little compared to frequencies on either side.

Dave, I've planned on implementing some Crowson transducers under my seating riser(s) for the last couple years, ... maybe you could beat me to the punch, no? By many accounts, the properly time aligned tactile transducer system blended with a killer acoustic transducer system is perma-grin material.

Scott knows of what he speaks, besides 5hz audibility begins somewhere around 110dB, ... tough stuff. Granted, if any room is ripe for it it's your wonderful room.

have you guys looked at the specs on the rotary sub? spl is only 115db or so...

Heheh. Like I've been saying for the past couple years. When in doubt.... quadruple.

Quote:

Originally Posted by FOH

Dave, I've planned on implementing some Crowson transducers under my seating riser(s) for the last couple years, ... maybe you could beat me to the punch, no? By many accounts, the properly time aligned tactile transducer system blended with a killer acoustic transducer system is perma-grin material.

Scott knows of what he speaks, besides 5hz audibility begins somewhere around 110dB, ... tough stuff. Granted, if any room is ripe for it it's your wonderful room.

This is the alternate choice and probably the better as it would save Dave a TON of money. A nice transducer system would be great to get that 10hz and down. Still, though, the signal chain roll off is very very critical here.

Living with an HT room that has a concrete floor, I'm thinking of doing just this. Most likely going to start with a bare riser and then add transducers all of which would be controlled by either a DCX or MiniDSP system.

Living with an HT room that has a concrete floor, I'm thinking of doing just this. Most likely going to start with a bare riser and then add transducers all of which would be controlled by either a DCX or MiniDSP system.

In case you're not already aware, be sure to put isolators under the riser to allow it to move and not mechanically short it to the slab.

In case you're not already aware, be sure to put isolators under the riser to allow it to move and not mechanically short it to the slab.

Hey thanks, Noah. Yeah, I have read a bit about it. Not a ton but it was recommended that I use some isolation feet of sorts. I have carpet that is medium to thick so I'll have to figure what's the best to get ....when I get around to it.

Right now my HT room is empty-ish as I transition. I don't want to thread crap on Dave's thread about it though.

5hz huh? Hmmm. That's a tricky area. Signal chain roll off is CRITICAL at this point. You MUST get this in line before anything else. Otherwise you're just throwing away money.

After that maybe think about a true rotary sub system. Anything resonant is not going to give you more 5hz and down, imo. At least, not worth the trouble imo.

My signal chain is pretty good down to 3hz, that is where roll off begins. No clone Amps here, I own the real thing.

Quote:

Originally Posted by FOH

Dave, I've planned on implementing some Crowson transducers under my seating riser(s) for the last couple years, ... maybe you could beat me to the punch, no? By many accounts, the properly time aligned tactile transducer system blended with a killer acoustic transducer system is perma-grin material.

Scott knows of what he speaks, besides 5hz audibility begins somewhere around 110dB, ... tough stuff. Granted, if any room is ripe for it it's your wonderful room.

I would need some quality transducers, as I already have 'buttKickers' and they make too much mechanical sound and distract me. So I turned them off. My other thought was to make a 1" riser and couple it too a couple of LMS 18" ultras????

Quote:

Originally Posted by LTD02

have you guys looked at the specs on the rotary sub? spl is only 115db or so...

Yes, I am very disapointed with the Rotary sub's output, so I won't be going that route.

Quote:

Originally Posted by Scott Simonian

Right now my HT room is empty-ish as I transition. I don't want to thread crap on Dave's thread about it though.

I would need some quality transducers, as I already have 'buttKickers' and they make too much mechanical sound and distract me. So I turned them off. My other thought was to make a 1" riser and couple it too a couple of LMS 18" ultras????

The Crowson transducers are, by all accounts, quality ... and way beyond the typical shakers.

I'm not sure where everyone is crossing them but I go that low because I have a nearfield sub from 30-80 for those frequencies. I probably have them crossed at 30 or 35, I would have to check.

I really need to do some serious testing with mine and get it just right. Every time I think I am going to do that I change something In the theater. Building a new baffle wall right now, if I had known what a job it was going to be I might have rethought it.